What does the 360-degree mark on a sine wave signify?

The 360-degree mark on a sine wave signifies the completion of one full cycle of the waveform. At this point in the cycle, the sine wave has returned to its starting position, which correlates with zero volts in a standard sine wave representation, following the periodic function of the wave. In a complete cycle, phases progress from positive peak to zero, to negative peak, and back to zero. Therefore, the point at 360 degrees aligns precisely with the moment when the waveform crosses the horizontal axis, indicating a voltage level of zero.

This understanding is key for analyzing AC waveforms, as identifying when the voltage is at zero is crucial for numerous applications, including timing in electrical cycles and phase relationships with other waveforms. In contrast, other points in the cycle would indicate peak positive or negative voltages, or an averaged output which does not represent the instantaneous value of the sine wave.